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It's not a regular car part, though. Ah, got it, it's the front clamp from an old wire ski binding - don't ask me how I know this, but I'm fairly sure no one else here can identify it.

"Do you know what this is?" comes a voice at my shoulder. I stand up, ready to reveal my disturbingly in-depth knowledge of ancient ski equipment, but before I can fix my features to smug, he continues, "It's from an old ski binding. The engineers were having difficulty holding the engine cover of the 910 down safely, and, over dinner one night, Mr Piëch spoke about this to his good friend Mr Geze, whose firm made these bindings, and this was the solution."

Dieter Landenberger is manager of Porsche's archives and a man who probably knows more about Porsche's history and heritage than the Porsche family themselves. This is fortuitous, as I'm currently in a warehouse containing many curious Porsches, most of which I'm struggling to identify. There is a reason I'm here. Porsche has a museum (if you haven't been and happen to find yourself in Stuttgart, go. It's amazing. Especially the escalator) but the 80 cars there are just the tip of a 500-strong iceberg. All of which have to be stored somewhere.

This is the somewhere. It's not far from the museum, just another industrial building in an industrial corner of an industrial city. It used to house a production line, but will soon store an entire back catalogue of automotive greatness (and not-so-greatness). I say soon because the ink on the lease is still wet. That's right, TopGear is here to help Porsche move its family jewels into a new home. Let's hope its insurance policy is up to date.

Big shiny trucks arrive, doors are opened, glimpses of cars appear and ramps are lowered. A man jumps on to a bright red Porsche tractor of considerable vintage and concours condition. There's a typically agricultural noise accompanied by a localised and particularly noxious fog cloud. When it clears, the tractor is revealed to be towing a totally see-through Cayenne Hybrid out from the transporter's interior. If Porsche were really concerned about CO2 emissions, this would surely be happening the other way round...

I lend a hand and loosen the ratchet strap on a Type 597 Jagdwagen military jeep. It lurches backwards, at which point some German expletives occur and I realise that old cars don't necessarily have effective handbrakes. Nor are they in perfect nick. Some are decidedly moth-eaten in fact, like the battered 906 that seems to have crashed headlong through each and every one of the 46 intervening years.

It looks properly battle scarred, all peeling bonnet badge, shagged upholstery and rotting composite panels. It's possibly my favourite car in the whole place, a story behind each ding and wrinkle. Dieter looks it over sympathetically and says: "It would be a shame to over-restore this car, we want to keep the authenticity of these cars alive. That, for us, is a big challenge."

I'm glad to hear him say it. Glad, too, that most of these cars are in less than pristine condition. The majority smell musty inside, dust is evident, they look like they've lived a bit. Or at least been in storage for a while. They jar with the polished floor and fresh paint that's been daubed around here. But this facility is evidence of how seriously Porsche takes its back catalogue. This, surprisingly, is a relatively recent phenomenon. The firm only started keeping the first and last cars from each production run a few years back. It's now making up for lost time by going on the open market and buying important cars back. It recently got hold of a 993 Cabrio. From Julio Iglesias. Yeah.

Not long ago, they found a car they'd completely forgotten about - a Porsche 924 made entirely of body filler. Not really, but that's what it looks like. Equipped with a 250-litre fuel tank, lightweight panels, a massive turbo and a primitive low-drag body it was intended to break speed and distance records, but Mercedes did something similar first, so Porsche hid this curiosity under an old blanket, behind a huge crate. And forgot about it.

There are other one-offs, too. The prototype 965, designed to fit between the 911 and the 959. That never saw the light of day. Nor the unique V8 engine inside it. There's a 968 Club Sport Cabrio, a ragtop 928, a latticework concept designed to test longevity (don't ask me how) and the Studie C88.

This last isn't really a Porsche at all, but the result of a competition the Chinese government held to design a car. "It only has one child seat because of the country's policy on children", Landenberger tells me, "and when we presented it, Dr Weideking [former CEO] learned his speech in Mandarin. But at the end it didn't help. The Chinese government said thank you very much and took the ideas for free, and if you look at Chinese cars now, you can see many details of our C88 in them."

There's some lovely personal stuff, too. The Porsche family order all their cars in the same forest-green shade, because it links to their love of hunting. There's the first ever 911 Turbo. It's unbadged with sports tartan trim down the flanks and was a birthday present for Louise Piëch (Ferdinand Porsche's daughter) in 1974.

Speaking of the Turbo, there's even a disguised version of the forthcoming 991 Turbo parked down the quiet end of the warehouse. I give it the once over, my eyes coming to rest on the keys left somewhat carelessly on the dash. World exclusive drive in the next Porsche Turbo, anyone?

I'd tell you to come here, but you wouldn't be allowed. Porsche is keeping this place secret. That's a great shame as these cars are as interesting as anything you'll see in the museum; they're just surrounded by slightly inferior architecture.

That will change, though, as Porsche intends to cycle these cars out to the museum, overseas shows, even rallies and races. And yes, even the one with the ski-binding boot clip.